Question on meaning of all Red and Black Flag

Have been seeing some all Red and Black Flag patches on multiple sites.

What is the meaning of these? Is this a FD "Thin Red Line" related thing?

Some kind of a "protest" thing?

Have thought about putting one on a vest because it matches some other patches and is kind of subdued in that manner but dont want to be disrespectful. (I would normally have words with someone from disrespecting the flag even in a patch)